# Electricity

#### Question 6:

A
copper wire has diameter 0.5 mm and resistivity of 1.6 × 10^{−8}
Ω
m. What will be the length of this wire to make its resistance 10 Ω?
How much does the resistance change if the diameter is doubled?

#### Answer:

Resistance
(*R*) of a
copper wire of length *l*
and cross-section *A*
is given by the expression,

Where,

Resistivity of coppe...

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